{
  "abstract": "The balance between sulfur and nitrogen (S-N) precursors influences secondary aerosol formation, yet its cross-phase links to particle composition and mixing states remain poorly constrained. Here, we integrated single-particle aerosol mass spectrometry (SPA-MS) with pollutant and meteorological observations during winter and summer emission control periods (ECPs) and corresponding normal periods (NPs) in Yangzhou, eastern China. By establishing gas-phase (gSNR), particle-phase (pSNR), and number-based (nSNR) sulfur-to-nitrogen ratio metrics, we combined causal inference with interpretable machine learning to analyze the underlying drivers. During ECPs, reduced NO x emissions alongside relatively stable SO ₂ concentrations elevated gSNR, driving an average ∼ 57 % increase in pSNR across particle classes and a 27 % expansion in mean vacuum aerodynamic diameter ( D va ) relative to NPs. Causal analysis revealed a stepwise propagation of S-N partitioning running sequentially from gas-phase precursors to single-particle chemistry and ultimately to the population mixing state. Particle-resolved chemistry demonstrated that pSNR enrichment was highest in particles containing both black carbon and organic carbon, but markedly lower in BC-free inorganic particles, indicating strong particle-type-dependent aging pathways. Relative humidity (RH) acted as a primary regulator of this cross-phase coupling: below 55 % RH, the SNR metrics decoupled, maintaining substantial chemical heterogeneity across particle classes (externally mixed state); above 85 % RH, aerosol liquid water uptake accelerated gas-particle exchange and multiphase processing, causing the SNR metrics to converge as aerosols evolve toward an internally mixed state. These findings suggest that future air-quality models would benefit from incorporating particle-type heterogeneity and humidity-dependent multiphase processes under shifting emission regimes.",
  "abstract_shown": true,
  "affiliations": [
    "Nanjing University of Information Science and Technology (Nanjing, China)",
    "Southeast University (Nanjing, China)"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 9,
  "authors": [
    {
      "name": "Yuan Dai"
    },
    {
      "affs": [
        0
      ],
      "name": "Junfeng Wang",
      "orcid": "0000-0001-6215-1953"
    },
    {
      "name": "Mindong Chen"
    },
    {
      "name": "Su Zhang"
    },
    {
      "name": "Haiwei Li"
    },
    {
      "name": "Yunjiang Zhang",
      "orcid": "0000-0002-4361-9685"
    },
    {
      "name": "Yun Wu"
    },
    {
      "name": "Ming Wang"
    },
    {
      "affs": [
        1
      ],
      "name": "Xinlei Ge"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/fpqhc323bb31w.bib",
  "cited_by": 0,
  "doi": "10.5194/acp-26-14015-2026",
  "fulltext_url": null,
  "id": "fpqhc323bb31w",
  "issns": [
    "1680-7324"
  ],
  "landing_url": "https://acp.copernicus.org/articles/26/14015/2026/",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "1902|Atmospheric chemistry and aerosols"
    ]
  ],
  "openalex": "W7220682822",
  "pdf_url": "https://acp.copernicus.org/articles/26/14015/2026/acp-26-14015-2026.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-06",
  "publisher": "Copernicus GmbH",
  "ris": "https://research.draconitic.com/paper/fpqhc323bb31w.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:34Z",
      "native_id": "10.5194/acp-26-14015-2026",
      "source": "crossref",
      "url": "https://acp.copernicus.org/articles/26/14015/2026/"
    }
  ],
  "subjects": [
    {
      "field": "earth",
      "origin": "openalex:1902|Atmospheric chemistry and aerosols",
      "subfield": "atmospheric"
    }
  ],
  "title": "Cross-phase partitioning of sulfur-nitrogen ratios and aerosol mixing-state evolution based on single-particle observations",
  "title_text": "Cross-phase partitioning of sulfur-nitrogen ratios and aerosol mixing-state evolution based on single-particle observations",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:20:34Z",
  "url": "https://research.draconitic.com/paper/fpqhc323bb31w",
  "venue": "Atmospheric Chemistry and Physics",
  "versions": [
    {
      "doi": "10.5194/egusphere-2026-3360",
      "pid": null,
      "relation": "preprint",
      "title": null,
      "venue": null
    }
  ]
}